The present invention is in the field of imaging systems. More particularly, the present invention provides an apparatus for delivering printing plates to an external drum imaging system.
In external drum imaging systems, a movable optical carriage is commonly used to displace an image recording source in a slow scan direction while a cylindrical drum, having recording media mounted on an external surface thereof, is rotated with respect to the image recording source. The drum rotation causes the recording media to advance past the image recording source along a fast scan direction that is substantially perpendicular to the slow scan direction.
The image recording source may include an optical system for generating one or more imaging beams that are scanned across the surface of the recording media. Each imaging beam may be separately modulated according to a digital information signal representing data corresponding to the image to be recorded.
The recording media to be imaged by an external drum imaging system is commonly supplied in discrete, flexible sheets, hereinafter collectively referred to as xe2x80x9cprinting plates.xe2x80x9d Each printing plate may comprise one or more layers supported by a support substrate, which for many printing plates is a plano-graphic aluminum sheet. Other layers may include one or more image recording (i.e., xe2x80x9cimageablexe2x80x9d) layers such as a photosensitive, radiation sensitive, or thermally sensitive layer, or other chemically or physically alterable layers. Printing plates that are supported by a polyester support substrate are also known and can be used in the present invention. Printing plates are available in a wide variety of sizes, typically ranging, e.g., from 9xe2x80x3xc3x9712xe2x80x3, or smaller, to 58xe2x80x3xc3x9780xe2x80x3, or larger.
A cassette is often used to supply a plurality of unexposed printing plates to an external drum imaging system. The printing plates are normally supplied in stacks of ten to one hundred, depending upon plate thickness, and are stored in the cassette. A plate manager may be used to automatically and selectively unload and feed a printing plate from a plurality of different cassettes to the external drum imaging system for imaging.
The emulsion side of the printing plates is extremely vulnerable to physical damage (e.g., scratches), which could render a printing plate unusable for subsequent printing. Accordingly, great care must be taken to avoid emulsion damage as each printing plate is separated from a stack of printing plates stored within a cassette, fed from the cassette into the external drum imaging system, and mounted onto the external drum for imaging. Unfortunately, preventing such damage has proven to be a very difficult and expensive task in currently available external drum imaging systems.
The invention is directed towards an apparatus for delivering a printing plate to an external drum platesetter and including: a plate traversing table for displacing a printing plate into a staging position; and a plate angling table, nested within the plate traversing table, for rotating the printing plate between the staging position and a loading position. The plate traversing table includes: a first shaft; a second driven shaft including a plurality of nip rollers; a plurality of pulleys mounted to the first and second shafts; a plurality of rotatable belts, extending between corresponding sets of the pulleys on the first and second shafts; and a drive system for rotating the driven shaft.